I have a junkyard pocket for my Westy's passenger door and I would use blue carpenter's chalk on the attaching surface of the pocket and then press it against the door in the right spot once that was determined.  Then mark the resulting hole areas with Sharpie, remove panel and use an awl for the pilot holes in those marked spots.
As with many of my projects, I might have overlooked something here but that is how I'd begin.
Stephen 

     On Wednesday, November 26, 2014 9:16 AM, Tom Buese <tantonbz@GMAIL.COM> wrote:
   

 So A dumb question-how do you line up the screw holes from the pocket on
the back side of the door panel?  It appears they need to be very exact-
vector analysis?

YMMV,

Mr. BZ-want to install used pocket in the doka which came w/ none & no holes

On Wed, Nov 26, 2014 at 6:10 AM, William Monk <billmonk@gmail.com> wrote:

> I like the aftermarket one busdepot offers..cheaper as well.
>

--
Tom Buese